Control valve for elastic pressure fluid

ABSTRACT

A control valve for elastic pressure fluid comprises a housing with inlet and outlet passages in which a valve member is movable from a first position in which pressure fluid is vented from one outlet passage to a second position in which pressure fluid is supplied to said outlet passage. A diaphragm formed as a cup shaped resilient disc divides the housing in two chambers, one of which being constantly vented to the atmosphere and the other being supplied with pressure fluid of varying pressure, the value of which causes the resilient disc to flex from a position in which the valve member is unaffected by the diaphragm to a position in which the valve member is moved from the one position to the other position.

United States Patent [1 [151 3,731,707

Berle et al. [451 Ma /8,1973

[54] CONTROL VALVE FOR ELASTIC 2,306,029 12/1942 Salzer ..25 1/75 XPRESSURE FLUID 3,542,289 11/1970 Ojala ..137/625.66

[75] 'v gx Antwerp'en; 3,559,945 2/1971 Comer ..251/75 X Lars GunnarNllsson, Hans Kristofler Olofsson, both at Wilrijk, all of Cary NelsAssistant Examiner-Robert J. Miller Belgium Attorney-Munson and Fiddler73 Assi nee: Atlas Co 0 Aktlebolag, Nacka, g Sweden pc ABSTRACT Acontrol valve for elastic pressure fluid comprises a housing with inletand outlet passages in which a valve [21] AWL 52,868 member is movablefrom a first position in which pressure fluid is vented from one outletpassage to a second position in which pressure fluid is supplied to [52]US. Cl ..137/625.66, 251/75 Said outlet passage A diaphragm f d as a cup[51] Int. Cl ..Fl6k 11/02 shaped resilient disc divides the housing intwo cham [58] Field of Search ..137/625.66, 625.26, 625.27, bets one ofwhich being constantly vented to the 137/625'61 625; 75 mosphere and theother being supplied with pressure fluid of varying pressure, the valueof which causes the [56] References Cited resilient disc to flex from aposition in which the valve UNITED STATES PATENTS member is unaffectedby the diaphragm to a position in which the valve member is moved fromthe one 3,601,151 8/ 1971 Brown l 37/625.66 position to the otherposition. 3,557,836 1/1971 Kutz ..l37/625.66 2,712,427 7/1955 Welborn eta]. v.251/75 X 5 Claims 1 Drawing Flgu" 2,288,642 7/1942 Powell ..251/75X Patented May 8,1973 3,131,101

l5 l7 l4 /9 l3 1/ AXEL GUNNAR BERLE, LARS GUNNAR NILSSON and HANSKRISTOFFER OLOFSSON INVENTORS BY MUNSON & FIDDLER,

Attorneys.

CONTROL VALVE FOR ELASTIC PRESSURE FLUID This invention relates tocontrol valves for elastic pressure fluid comprising a housing, inletand outlet passages in said housing, a valve member in the housing whichvalve member is movable from a first position, in which pressure fluidis vented from one of said outlet passages to a second position, inwhich pressure fluid is supplied to said one outlet passage. Controlvalves of this type are frequently used as unloading valves for motorcompressor units and other compressors and for controlling compressedair for extinguishing electric arcs in electric switches and for otherpurposes. The conventional valves are complicated and often unreliablein operation and expensive and one object of the invention is to avoidthese disadvantages. The control valve according to the inventioncomprises a housing forming a first and a second chamber separated by adiaphragm comprising a cup shaped resilient disc, which in a firstdeflected position makes equilibrium against a fluid pressure in saidfirst chamber and a force independent of said fluid pressure, and whichupon increase of said fluid pressure over a predetermined value isdeflected and snaps over to a second opposite position in which saiddiaphragm moves said valve member to said second position, in whichpressure fluid is supplied to said one outlet passage. Other features ofthe invention will be evident from the following specification and theappended claims.

On the enclosed drawing one embodiment of a control valve according tothe invention is illustrated by way of example, the FIGURE being anaxial section through said control valve.

The illustrated control valve comprises a' housing which consists ofthree parts, an upper part 1, an intermediate part 2, and a lower part3, preferably bolted together. The illustrated control valve is intendedto be used as an unloading valve in a motor compressor unit. The upperpart 1 of the housing forms an inlet passage 5 which, when the valve isused as above indicated, is supplied with pressure fluid from thecompressor receiver or other part of the compressed fluid network at thedischarge side of the compressor. The pressure supplied to the passage 5may preferably be a reduced delivery pressure or may stand in certainrelation to pressure changes in a compressed fluid network which is fedby the compressor. The housing 1 3 is further provided with an inletpassage 6 in the lower part 3 of the housing which inlet passage may besupplied with pressure fluid for operation of an unloading mechanism ofthe compressor, and for this purpose said passage may preferably beconnected to the delivery end of the compressor or to a receiver fed bythe compressor. In the intermediate part 2 of the housing an outletpassage 7 is formed which may be connected to and communicates with anunloading mechanism of the compressor. The valve housing is,furthermore, provided with a vent passage 8 which may communicate withthe atmosphere. The pressure fluid which is supplied to the inletpassages 5 and 6 may naturally be another pressure fluid than compressedair from an air compressor receiver in cases where the control valvedevice is used for other purposes than as an air compressor unloadingvalve.

The upper part 1 and the intermediate part 2 of the housing form a firstchamber 1 1 and a second chamber 12. The pressure fluid supply from theinlet passage 6 to the outlet passage 7 is controlled by the doublevalve member 9, 10 which is disposed in the intermediate part 2 of thehousing. The first chamber 11 communicates with the inlet passage 5 andthe second chamber 12 continuously communicates with the atmospherethrough an outlet passage 8. The chambers 11 and 12 are separated by adiaphragm comprising a cup shaped resilient disc 13 which in theillustrated embodiment consists of an annular frusto'conical metalspring disc, the central portion of which is sealed against a springretainer 14 which in the figure is pressed downwards by a helical spring15. The annular disc 13 rests on a seat 16 at the lower face of thespring retainer 14 and a sealing ring 17, such as an O-ring, is providedbetween the inner annular portion of the disc and the spring retainer.The outer portion of the disc 13 rests on a ring 18 which forms a seatfor the outer portion of the disc, and a sealing ring 19, such as anO-ring, is provided at the upper side of the outer portion of the discbetween said portion and the upper part 1 of the housing. The seat 16 isformed in such a way that the outer edge of the disc 13 is free to moveradially inwards due to the provision of a space or clearance 20 andsimilarly the seat 18 is carried out in such a way that the peripheralouter edge of the disc 13 is free to move radially outwards due to theprovision of a clearance 21. The spring retainer 14, the seat formingring 18, and the valve member 10 may preferably be carried out by aresinous material, for instance a material sold under the trade markDELRIN.

The helical spring 15 is inserted between the spring retainer 14 and ascrew threaded spring retainer 22 which is engaged by a set screw 23.The set screw 23 has a flange 24 which bears on a counter bore in theupper part 1 of the housing and the set screw is accessible foradjustments through a bore 26 in the upper part 1 of the housing inwhich bore the screw head 25 is accessible from the outside of thehousing. An O-ring 27 forms a seal between the set screw 23 and theupper part 1 of the housing. By means of the set screw 23 the tension ofthe spring 15 may be adjusted and since the spring 15 and the fluidpressure in the first chamber 11 act against the spring force producedby the annular disc 13 said adjustment of the spring 15 defines thefluid pressure in the inlet passage 5 at which the annular spring disc13 is deflected to. its lower position.

The valve members 9, 10 cooperate with seats 28, 29 on the intermediatepart 2 of the housing and the valve members 9, 10 are connected one withthe other by means of a spindle 30 which with certain clearance extendsthrough a bore 31 in the intermediate part 2. The bore 31 communicateswith the outlet passage 7. A helical spring 32 is provided between thevalve member 10 and a plug 33 which is screwed into a threaded portionof a bore 34 provided in the lower part of the housing and in theintermediate part 2. The bore 34 communicates with the inlet passage 6.In the bore 34 the valve member 10 and spring 32 and a number of shims35 for adjustment of the spring tension are disposed. The tension of thespring 32 defines the difference in pressure between the reloading andunloading pressure of a compressor and may be adjusted by suitablechoice of the number and thickness of the shims 35 between the spring 32and the plug 33. V

The control valve device above described and used as unloading valveoperates in the following manner:-

The inlet passage 5 normally communicates with a pressure fluid source,for instance the receiver of an air compressor, so that air pressurecorresponding to the receiver pressure or to a change in the receiverpressure prevails in the first chamber 11. The inlet passage 6 ispreferably in communication with the receiver of the compressor oranother part of a compressed air network for the supply of operatingair. The outlet passage 8 forms a constant communication between thesecond chamber 12 and the atmosphere so that the second chamber 12 isalways vented. The outlet passage 7 preferably communicates with anunloading mechanism for the compressor which may operate so that whenoperating air is supplied through the outlet passage 7 the compressor isunloaded. The annular resilient disc 13 has such spring characteristicthat the spring force at first rises when the disc is pressed downwardsfrom the illustrated position, said spring force increasing to a certainmaximum and then decreases when the spring disc is flattened. The springforce of the disc then decreases still further but is still directedupwards also when the spring disc has snapped down so that it isdeflected downwards in the figure. The spring force decreases howevercontinuously within the control range of the device from the abovementioned maximum value. In the figure the control valve according tothe invention is illustrated in the position which it takes when thecompressor is in operation and loaded. If the pressure on the deliveryside of the compressor, i.e. in the receiver, rises then the pressure inthe inlet passage 5 will also rise and consequently also the pressure inthe first chamber 11 and this pressure together with the force of thespring 15 presses the resilient disc 13 downwards in the figure so thatsaid disc is gradually flattened. When the pressure in the inlet passage5 and the chamber 1 1 increases to a certain value then the upwardsdirected spring force of the disc 13 first increases to a maximum. Asmentioned hereinabove the upwards directed force of the resilient discthen decreases as the disc is flattened and if the pressure in thechamber 11 rises further then the disc 13 is quickly swung down by saidforce so that the disc 13 is deflected downwards in the figure. Thespring retainer 14 then abuts the valve member 9 and forces said membertowards the seat 28 against the action of the spring 32. The valvemember 10 is then lifted from its seat and operating air from the inletpassage 6 flows through the bore 34 and the bore 31 to the outletpassage 7 and further to the unloading mechanism of the compressor, sothat the compressor is unloaded, for instance by the inlet valves beingkept open by the unloading mechanism.

The compressor remains unloaded as long as the pressure in the firstchamber 11 and the force of the helical spring is greater than theupward spring force of the resilient disc 13 plus the force of thespring 32 which through the valve member 9 acts on the spring retainer14. During this interval the compressor runs unloaded. When the pressureon the discharge side of the compressor or in the receiver,respectively, again decreases to a certain other value than theunloading value then the force of the spring disc 13 and the force ofthe spring 32 will move the spring retainer 14 upwards in the figure anddue to the spring characteristic of the resilient disc 13 the springretainer and diaphragm snaps up to the position illustrated in thefigure in which the resilient disc 13 is deflected upwards.Simultaneously, the valve member 10 closes the communication between theinlet passage 6 and the outlet passage 7 and the valve member 9 opensthe communication between the outlet passage 7 and the chamber 12 andthe vent passage 8 so that the unloading mechanism of the compressor isvented and the compressor is reloaded. By changing the pre-tension ofthe spring 32, i.e. by changing the number of shims 35, the reloadingpressure of the compressor i.e. the difference between reloading andunloading pressure is changed.

The embodiment of the invention above described and illustrated on thedrawing should only be considered as an example and may be modified invarious different ways within the scope of the claims. The control valvedevice according to the invention may, for instance, be utilized tooperate on other pressure fluids than compressed air delivered by thecompressors for operation of the unloading mechanism or other mechanismsand it may also be used for other purposes than above described.

We claim:

1. A control valve for elastic pressure fluid comprising, a housing,inlet passages and outlet passages in said housing, a valve member inthe housing which valve member is movable from a first position, inwhich pressure fluid is vented from one of said outlet passages to asecond position in which pressure fluid is supplied to said one outletpassage, said housing forming a first and a second chamber separated bya diaphragm consisting of a cup-shaped resilient disc which in a firstdeflected position makes equilibrium against a fluid pressure in saidfirst chamber and a force independent of said fluid pressure, and whichupon increase of said fluid pressure over a predetermined value isdeflected and snaps over to a second opposite position in which saiddiaphragm moves said valve member to said second position, saidresilient disc comprising a spring characteristic curve which whendeflected away from said first deflected position towards said secondopposite position has a maximum spring force and a reduced spring forcewhen the disc is in snap-over position, and a still more reduced springforce when the disc is deflected further towards said second oppositeposition, said spring force being directed in the same direction.

2. A control valve according to claim 1 in which the cup shapedresilient disc is an annular frustoconical spring disc, and in which aspring retainer is provided which forms a seat for the inner border ofsaid annular disc and is sealed against the disc, which is furthermoresealed against the housing at the outer border.

3. A control valve according to claim 2, in which an adjustable helicalspring is provided in the housing and presses said spring retainer inthe same direction as the fluid pressure on the diaphragm.

4. A control valve according to claim 2, in which the outer and inneredges or borders of the resilient annular disc are mounted in thehousing so that they are free to move radially.

S. A control valve according to claim 1, in which the valve member ismovable from said first position to said second position against theforce of a spring, the tension of which is adjustable by means of one ormore shims. 5

1. A control valve for elastic pressure fluid comprising, a housing,inlet passages and outlet passages in said housing, a valve member inthe housing which valve member is movable from a first position, inwhich pressure fluid is vented from one of said outlet passages to asecond position in which pressure fluid is supplied to said one outletpassage, said housing forming a first and a second chamber separated bya diaphragm consisting of a cup-shaped resilient disc which in a firstdeflected position makes equilibrium against a fluid pressure in saidfirst chamber and a force independent of said fluid pressure, and whichupon increase of said fluid pressure over a predetermined value isdeflected and snaps over to a second opposite position in which saiddiaphragm moves said valve member to said second position, saidresilient disc comprising a spring characteristic curve which whendeflected away from said first deflected position towards said secondopposite position has a maximum spring force and a reduced spring forcewhen the disc is in snap-over position, and a still more reduced springforce when the disc is deflected further towards said second oppositeposition, said spring force being directed in the same direction.
 2. Acontrol valve according to claim 1 in which the cup shaped resilientdisc is an annular frusto-conical spring disc, and in which a springretainer is provided which forms a seat for the inner border of saidannular disc and is sealed against the disc, which is furthermore sealedagainst the housing at the outer border.
 3. A control valve according toclaim 2, in which an adjustable helical spring is provided in thehousing and presses said spring retainer in the same direction as thefluid pressure on the diaphragm.
 4. A control valve according to claim2, in which the outer and inner edges or borders of the resilientannular disc are mounted in the housing so that they are free to moveradially.
 5. A control valve according to claim 1, in which the valvemember is movable from said first position to said second positionagainst the force of a spring, the tension of which is adjustable bymeans of one or more shims.